This invention relates to a means for binding wire around objects, for example bales of fiber material.
Pulp bales are bound around both individually and in the form of stacked units comprising a certain number of bales, usually six or eight bales. Such a unit load has a weight of between one and two tons. The strength of the wire binding tying together the unit load, therefore, is very important from a safety point of view, because several persons may stand near the load while it is being lifted by its wires. The equipment used for tying the knot in a bound wire loop and the knot itself, therefore, are subject of very comprehensive safety regulations and stringent safety controls.
The binding means comprises a unit for feeding the wire from a wire magazine through an openable wire guide bar around the object.
The feeding unit is used also for stretching the wire. The means comprises further a twining member, which includes a unit for locking the wire end, a unit for tying a wire knot, a cutting unit and a unit for projecting the knot.
The wire guide bar extends around the object to be bound and guides the wire at its feed. The wire is fed through the twining member around the object to be bound. When the free end of the wire arrives for the second time at the twining member, the wire is stopped and retained in the locking unit, whereafter the wire is stretched by reversing the feeding unit. The wire guide bar is thereby opened, and the wire is tightened around the object to be bound. The knot is tied, the wire is cut and projected out of the twining member.
In order to achieve an optimum binding and knot-tying result, the correct length of wire must be fed. The wire normally is fed by means of a feeding wheel, which rotates through a predetermined number of revolutions and is driven, for example, by an electric servomotor. The feeding wheel is used also for stretching the wire.
In the wire magazine, on the path of the wire from the wire magazine to the feeding wheel, and in the wire guide bar, however, the wire can jam, whereby sliding can be caused between the feeding wheel and wire. Problems can also arise by variations in the wire quality, in its thickness and hardness, which result in sliding between the feeding wheel and wire.
The sliding creates problems during the feeding. The positions of the wire then cannot be determined, which may cause breakdowns. When then for avoiding sliding the contact pressure from the counter-pressure rolls is increased, there is risk of wire deformation whereby the feed of the wire through the different units in the binding means is made difficult.
The present invention offers a solution of the aforesaid problems, in that the measuring of the fed wire length takes place in a separate measuring means, which is not affected by sliding in the feeding wheel.
The characterizing features of the invention are apparent from the attached claims.